Electromagnets

We defined POWER as the RATE of doing work. The actual work or capacity to do
work is called
ENERGY
. Energy can be Kinetic (dynamic), Potential (static), or Radiant
(electromagnetic) in nature. Energy, according physical law of "Conservation
of Energy", is never lost nor gained. It may be changed from one form to
another, but it never just "disappears". Just like in our resistor, we had
energy being used which was dissipated as heat. The electrical energy was
transformed into heat energy. It didn't disappear, it merely changed form.
There are many other forms of energy. Some other forms of energy are light,
sound, momentum, and
MAGNETISM
.

We are all familiar with magnets, and their peculiar properties which make them
seem almost magical. A magnet can be used to hold a screw onto a screwdriver,
to lift a car, or find your way in the forest. But what is it that makes a
magnet do what it does?

If we take a magnet, and mark one end of it, we can identify one end from the
other. If we then suspend the magnet from a string, so that it is free to
rotate, we will notice that one end will ALWAYS point toward the north, and
that it will ALWAYS be the same end of the magnet that points north.

From this, we have concluded that there is a
NORTH POLE
and a
SOUTH POLE
on every magnet. Typically the north pole is marked with an N, and south pole
is marked with an S.

Now if we take two magnets with known, marked poles, and bring the North Pole
of one magnet close to the South Pole of the second magnet, the two magnets
will PULL TOWARD one another until they are connected. If we reverse the
experiment, and bring the North Pole of one magnet, near the North Pole of the
second magnet, they will PUSH AWAY from each other.
This effect is called the
LAW OF POLES
which states:

Why is it that magnets act this way? And why do magnets have poles? These are
questions which science has found difficult to answer. It is believed, though,
that according to the
Molecular Theory of Magnetism
inside of all magnets, the tiny molecules that the magnet are made of, are all
little tiny magnets in themselves, and that they are all lined up in a row.

In a normal piece of steel, for instance, the molecules are arranged in random
order, with positive and negative poles scattered about in all directions.

But when magnetized, the tiny magnetic molecules line up, allowing the whole
piece of steel to act like one big magnet.

If we place a magnet beneath a piece of paper, and place iron filings on top
of the piece of paper, the result would look something like the example to the
right. The iron filings will arrange themselves to LOOK like the invisible
magnetic force which surrounds the magnet. This invisible magnetic force which
exists in the air or space around the magnet, is known as a
MAGNETIC FIELD
, and the lines are called
MAGNETIC LINES OF FORCE
.

Now if we take a non-magnetic object, such as a glass rod, and place it
within the path of a magnetic field, the lines of force produced by the field
would pass right through the object.

If, however, we wrap a magnetically conductive layer around the object, such
as a soft iron, the iron will cause the lines of force to bend, and go around
the object instead of through it. This is called a
SHIELDING
effect.

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